Given their large storage capacity, non-contact readout, ability for high-speed access and other merits, optical disks are being used today in numerous applications. including optical disks for digital data, CD-ROMs, ROMs, compact disks and video disks.
Transparency is a key feature required in the optical substrate of such optical disks, as well as in optical fibers. lenses and supplies for lighting implements. In optical substrates in particular, not only must these have a high light transmittance in the regenerated laser light wavelength region, they must also have the property of transmitting light of wavelengths extending from the visible region to the infrared region.
Properties such as low water absorbance and heat resistance are also required. Polycarbonate resins [A] are commonly used as plastic materials which satisfy these properties.
However, in Prior-art Polycarbonate resins [A] coloration sometimes occurs during molding, as a result of which the polycarbonate [A] resin substrates, lenses and the like obtained have an inferior transparency.